Switch adapter structure for a dust-ignition-proof enclosure

ABSTRACT

An adapter structure which will permit standard switch operators of the oil tight type to be used in dust-ignition-proof enclosures. The adapter permits the switch operator to be mounted on the outside surface of a door to actuate a switch mounted on the inside surface of the door and provides a structure which will exclude ignitable amounts of dust or amounts which might affect performances or ratings of devices within the enclosure and will not permit arcs, sparks or heat otherwise generated or liberated inside of the enclosure to cause ignition of exterior accumulations or atmospheric suspensions of a specified dust on or in the vicinity of the enclosure.

United States Patent Lehman et al.

[4:] Aug. 1, 1972 [54] SWITCH ADAPTER STRUCTURE FOR A DUST-IGNITION-PROOF ENCLOSURE [72] Inventors: Lewis M. Lehman; John A. Koeppler, both of Milwaukee, Wis.

[73] Assignee: Square D. Company, Park Ridge, 111.

[22] Filed: Oct. 2, 1970 [21] Appl. No.: 77,549

[52] US. Cl ..200/l68 (3,200] 172A [51] Int. Cl. ..H01h 9/04 [58] Field of Search ..200/l68 G [56] References Cited UNITED STATES PATENTS 3,264,443 8/1966 Farina et al. ..200/ 168 G X 3,315,060 4/1967 Rothweiler et al ..200/167 A 3,305,660 2/1967 Sohns et al. ..200/172 R 3,213,213 1 1965 De Smidt ..200/l68 G X 3,472,986 10/1969 Stallman ...............200/l68 G X 3,246,110 4/1966 l-lermanson et al. ..200/l68 G X Primary Examiner-H. 0. Jones Attorney-Harold J. Rathbun and William H. Schmeiling ABSTRACT An adapter structure which will permit standard switch operators of the oil tight type to be used in dust-ignition-proof enclosures. The adapter permits the switch operator to be mounted on the outside surface of a door to actuate a switch mounted on the inside surface of the door and provides a structure which will exclude ignitable amounts of dust or amounts which might affect performances or ratings of devices within the enclosure and will not permit arcs, sparks or heat otherwise generated or liberated inside of the enclosure to cause ignition of exterior accumulations or atmospheric suspensions of a specified dust on or in the vicinity of the enclosure.

10 Claims, 4 Drawing Figures PATENTED M 1 SHEET 2 [IF 2 INVENTOR LEW/S M LEHMA/V JOHN A KOEPPLF/P SWITCH ADAPTER STRUCTURE FOR A DUST- IGNITION-PROOF ENCLOSURE This invention relates to enclosures for electrical devices and is more particularly concerned with an adapter structure which will permit standard switches and switch operators of the oil tight type to be used in enclosures classified as dust-ignition-proof type enclosures.

The National Electric Code requirements dictate that electrical devices within enclosures classified as Dust-ignition-proof shall be enclosed in a manner which will exclude ignitable amounts of dust or amounts which might affect the performance or rating of the devices and which, when installation and protection are in conformance with the code, will not permit arcs, sparks or heat otherwise generated or liberated inside of the enclosure to cause ignition of exterior accumulations or atmospheric suspensions of a specified dust on or in the vicinity of the enclosure.

For the purposes to testing and providing a basis for rating enclosures, various atmospheric mixtures have been grouped on the 'basis of their hazardous characteristics, such as Group E which includes atmospheres containing metal dust including aluminum magnesium and their commercial alloys and other metals of similarly hazardous characteristics, Group F which includes atmospheres containing carbon black, coal or coke dust and Group G which includes atmospheres containing flour, starch or grain dusts. One method of determining if an enclosure is considered acceptable for use in "Dust-ignition Proof atmospheres of the Groups indicated is to simulate the heating and cooling of the devices which may be mounted within the enclosure for a specified number of cycles while the enclosure is surrounded by circulating magnesium dust-air mixtures. In order to successfully pass the tests, no ignition of the magnesium dust outside of the enclosure may occur during the test and at the conclusion of the test, upon disassembly, no magnesium dust may be found to have entered the enclosure.

Heretofore, enclosures intended for dust-ignitionproof applications usually were constructed of heavy cast metal parts having precision ground mating surfaces which were bolted together. Additionally, when manually operated switches were included in the cast enclosures, the operators for the switches were required to extend through machined openings in the walls forming the enclosure. Thus the cast metal enclosures which were furnished to satisfy the requirements of dust-ignition-proof installations were limited in the number of sizes which could be economically furnished and were heavy, relatively expensive, and decidedly limited in the number of manual switch arrangements which could be accommodated.

For the last several decades, manufacturers of industrial control type equipment have been supplying complete lines of manually operated switches known as oil-tight to the trade. The oil-tight type switching devices usually include a linearly or a rotatably movable operator which is mounted on the external surface of a sheet metal panel and one or more switching units which are positioned on the internal surface of the panel to be actuated by movement of the operator through the opening in the panel. The operator usually is provided with a sealing arrangement which prevents the entrance of fluids through the opening in the panel.

acceptable to prevent fluids from entering enclosures, they per se are unacceptable for use in dust-ignitionproof enclosures because the seals used in the operators are considered incapable of keeping dust from entering the enclosure or preventing hot gases from escaping from within the enclosure and causing ignition of exterior accumulations or atmospheric dust suspensions on or in the vicinity of the enclosure.

it is an object of the present invention to provide a structure which will permit a standard type oil-tight switch operator to be used in an enclosure classified as a dust-ignition-proof enclosure.

An additional object is to provide a dust-ignitionproof enclosure with a panel member and a switching assembly including a unitary switch operator that is mounted on the exterior of the panel member, a unitary switch that is mounted on the interior of the panel member and a means for mounting the operator and the switch on the panel member to provide an operative connection between the operator and the switch and permit the enclosure to be classified as a dust-ignition-proof enclosure which is suitable for use in certain designated atmospheres.

A further object is to provide an adapter structure which, when used with a standard oil-tight pushbutton and a selector switch operator, will permit the operator to be used in enclosures that are classified as dust-ignition-proof.

Further objects and features of the invention will be readily apparent to those skilled in the art from the specification and appended drawing illustrating certain preferred embodiments in which:

FIG. I is a side elevational view of the switching assembly incorporating the features of the present invention which may be used in an enclosure classified as dust-ignition-proof.

FIG. 2 is a front view of the switch structure in FIG. 1.

FIG. 3 is a side view of the assembly in FIG. 1 rotated with a certain portion of the assembly shown in cross section.

FIG. 4 is a perspective view of the components of the switching assembly in F IG. 1 as exploded.

in the drawing, a numeral 10 indicates a portion of a panel member which is part of an enclosure for electrical devices classified as dust-ignition-proof for atmospheres specified by the National Electric Code. The panel member 10 preferably is formed of sheet metal and provides the cover for the enclosure and is secured to the base of the enclosure by suitably spaced bolts which, when tightened, will compress suitable and approved gasket material between the cover and the base to effect a dust-tight connection therebetween. The panel member 10 provides a portion of an internal wall 12 and an external wall 14 of the enclosure and has a pair of spaced openings 16 and 17 extending therethrough.

Positioned on the panel member 10 are a pair of switches 18 and 20, a switch operator 22 and a means 24 which acts as an adapter to mount the switches 18 and 20 and the switch operator 22 on the panel member 10 in a manner which will permit the enclosure to be classified as dust-ignition-proof. The switches 18 and 20 shown in the drawing are merely illustrative of the type of switch or switches which may be used in the combination and are of the type fully disclosed in the US. Pat. No. 3,336,455 which was granted to the inventors Merlin Y. Turnbull, Josef Bierenfeld and Carl B. Sohns on Aug. 15, 1967.

As the switches 18 and 20 are identical, only the components of the switch 18 will be identified, it being understood that similar components of the switch 20 will be identified by a suffix letter following the identifying numbers used to designate the components of the switch 18.

The switch 18 includes a housing 26 and a plunger 28. The housing 26 includes two pairs of wire connecting terminals 30 and 32 with the terminals of each pair connected to stationary contacts that are positioned within the housing 26. The plunger 28, which is movable along a linear axis between two positions within the housing 26, carries movable contacts which are arranged to complete a circuit between the pair of terminals 30 shown in FIG. 1 when the plunger 28 is positioned as in FIG. 3. When the plunger 28 is moved inwardly in the housing 26 from the position shown in FIG. 3, a circuit will be completed between the pair of terminals 32 shown in H6. 1. The switch 18 also includes a pair of openings which will receive a pair of mounting screws, one of which is shown in FIG. 3, and identified by a numeral 34.

The switch operator 22, as illustrated, is of the type disclosed in the US. Pat. No. 3,370,48l which was granted on Feb. 27, [968 to the inventors Earl F. Mekelburg and Howard P. Stock without the interlock mechanism shown in the Mekelburg et al patent. The switch operator 22 also may be any suitable oil-tight type, as, for example, the non-illuminated versions of the operators disclosed in the following United States patents which were granted to the inventors on the dates indicated:

As disclosed in the Mekelburg et al patent supra, the switch operator includes a housing 36 and a pair of operator members 38 and 40 respectively having stem portions extending through a pair of spaced bores in the housing 36. The stem portions on the operators are axially movable in the bores and are biased by springs, not shown, to position the operators 38 and 40 as in FIG. 3, and permit the operators 38 and 40 to move to the right from the position shown. The housing 36 has threaded openings 46 extending in four quadrantly located bosses which provide a rear mounting surface 50 for the housing. The housing 36 also has a forwardly facing annular flange surface 52. Extending forwardly of the flange surface 52 is a threaded portion, not shown, whereon a threaded ring nut 54 is positioned. A portion 56 on the housing 36 projecting forwardly of the ring nut 54 separates the portions 58 and 60 on the respective operating members 38 and 40. The portions 58 and 60 project forwardly of the ring nut 54 and provide end surfaces 62 and 64 that are accessible for manual manipulation while the guard portion 56 protects against accidental simultaneous actuation of the operators 38 and 40. Surrounding the stern portions of the operators 38 and 40 are seals 66 which prevent and dust from entering an annular cavity 68 extending inwardly in thehousing 36 from an open rear end of the housing 36. The operating members 38 and 40 have operating end portions 70 and 72 located within the cavity which are respectively aligned with the plungers 28 and 28a on the switches l8 and 20 when the switches 18 and 20 and the switch operator 22 are mounted on the panel member 10 in a position wherein the plungers 28 and 28a are aligned with the centers of the openings 16 and 17 by the adapter means 24.

As most clearly shown in FIG. 4, the adapter means 24 includes an inside mounting member 74, an outside mounting member 76, a pair of bushings 78 and 80, a pair of pin-like plungers82 and 84, a collar 86, and a pair of seals 88. The member 76 is generally cylindrical in shape and has a threaded side wall 94 and a flat rear surface or wall 96 which engages the external wall 14. A front wall 98 of the member 76 has a cylindrical depression 100 therein and extending from the rear wall of the cylindrical depression 100 to the rear wall 96 are a pair of openings 102 and 104 which have threaded walls and are located to be aligned with the openings 16 and 17 when the member 76 is positioned on the external wall 14. The member 76 is sized and the openings 102 and 104 are located so that a large metalto-metal surface contact exists between the portions of the member 76 and the external wall 14 that surrounds the openings [02 and 104 to satisfy the requirements specified by the Code making authorities concerned with the equipment to which this invention relates.

The member 74 also is cylindrical in shape and includes a front flat surface 106 which is positioned with an intimate metal-to-metal contact on the internal wall 12. A rear surface 108 of the member 74 is provided with a cylindrical depression 110 and four internally threaded openings 112 which receive the mounting screws 34 for the purpose of mounting the switches 18 and 20 on the rear surface 108. Extending between the front wall of cylindrical depression 110 and the rear surface 108 are a pair of openings 114 and 116 which are aligned with the openings 16 and 17 on the panel member 10 when the member 74 is positioned on the internal wall 12. EAch of the bushings 78 and 80 is provided with a flange or collar 1 18 on one end, a threaded portion extending from the collar 118 to the other end of the bushing and a bore [24 extending axially through the bushing and concentric to the threaded portions 120. The bushings 78 and 80 extend through the openings 16 and 17 and are used to secure the member 74 in its proper position adjacent the internal wall 12 and the member 76 in its proper position adjacent the external wall 14. The bushings 78 and 80 have their threaded portions 120 received in the threaded openings 102 and 104 and their collar portions 118 engaging the rear wall of the cylindrical depression 110 to secure the members 74 and 76 on the panel member l0. When the members 74 and 76 and the bushings 78 and 80 are thus positioned on the panel member 10, the bores 124 in the bushings 78 and 80 will be aligned with the plungers 28 and 28a and the operating ends 70 and 72 ofthe switch operator 22. The plungers 82 and 84 are positioned within the bores 124. Each of the plungers 82 and 84 has a headed portion 26 engaging the operating ends 70 or 72 and a free end 128 positioned to engage the free end on the plungers 28 or 28a and thus will transmit movement of the operators 138 and 40 to the plungers 28 and 28a when either of the operators 38 or 40 are moved toward the panel member 10. The headed portions 126 are provided on the plungers 82 and 84 to maintain the plungets 82 and 84 captive in the event the switches 18 and 20 are removed for service purposes. The plungers 82 and 84 are sized to provide minimum clearance between the walls of the bores 124 to limit the passage of hot gases and ign-itable dust from the interior of the enclosure to the exterior of the enclosure.

The member 74 also is sized and the openings 114 and 116 are located so that a large metal-to-metal surface contact exists between portions of the member 74 and the internal wall 14 that surrounds the openings 114 and 116 to satisfy the requirements of the codemaking authorities concerned with the equipment to which this invention relates.

The collar 86 is formed as an internally threaded ring having an inwardly extending flange 130 on one end. The panel member as illustrated is preferably formed of sheet metal, having a gauge thickness sufficient to comply with the requirements of the codemaking authorities concerned with the equipment to which the present invention relates. it is also contemplated that the switch operator 22, the switches 18 and as used with the adapter means according to the present invention, may be used in enclosures formed of materials other than sheet metal, for example, a suitable organic plastic material which exhibits the proper strength and heat resistance and other properties required to satisfy the requirements of the code making authorities concerned with the equipment to which this invention relates.

The switching assembly including the switches 18 and 20, the switch operator 22 and the adapter 24 may be readily installed on the panel member 10 by positioning the member 74 on the internal wall 12 and the member 76 on the external wall 14 with the openings 4 and [16 in the member 74 and the openings 102 and 104 in themember 76 aligned with the openings l6 and 17. The bushings 78 and 80 secure the members 74 and 76 on the panel member 10 when they are threaded into the openings 102 and 104 in a manner so the flanges thereof engage the front wall of the circular depression 110. If desired, an adapter 132, which if fully disclosed in the Turnbull et al patent, is positioned between the rear surface 108 and the switches 18 and 20 for the purpose disclosed in the Turnbull et al patent. The switches 18 and 20, as well as the adapter 132, are secured on the rear surface 108 when the screws 34 are threaded into the threaded openings 112. The plungers 82 and 84 are installed in the bores 124 with the headed portions 126 engaging the threaded ends of the bushings 78 and 80. After the plungers 82 and 84 are thus positioned, the switch operator 22 is positioned on the front wall 98. The switch operator is indexed and maintained against rotation on the front wall 98 by a pair of pins 134 which are immovably secured in suitable openings in the front wall 98 and are received in the openings 46. The position of the switch operator 22 on the front wall 98 is maintained by the collar 86. The collar is threaded upon the threaded side wall 94 until the flange is pressed into tight engagement with the seals 88 to provide a fluid and dust-tight connection between the switch operator 22 and the collar 86. After the collar 86 has been thus positioned on the member 78, if desired, a suitable plate 136 bearing instructional information such as "START-STOP" is positioned on the threaded portion of the operator housing. The plate 136 is maintained in its position when the ring nut 54 is threaded into its proper position on the switch operator 22 to complete the assembly.

While certain preferred embodiments of the invention have been specifically disclosed, it is understood that the invention is not limited thereto, as many variations will be readily apparent to those skilled in the art and the invention is to be given its broadest possible interpretation within the terms of the following claims.

What is claimed is:

1. In an enclosure for electrical devices, the combination comprising: a panel member providing the enclosure with an external front surface and an internal rear surface, said panel member having an opening extending between the surfaces, a first member having a flat front surface engaging portions of the internal rear surface surrounding the opening and an opening extending therethrough aligned with the opening in the panel member, a switch including a housing mounted on a rear surface portion of the first member and, a plunger having a free end spaced rearwardly of the opening in the panel member and movable from a first position to a second position along an axis extending through the opening in the panel member, a second member including a flat rear surface engaging portions of the external surface of the panel member surrounding the opening in the panel member, a front surface spaced forwardly of the front surface of the panel member, an externally threaded peripheral surface extending between the front surface and the rear surface, and an opening extending between the front surface and the rear surface axially aligned with the opening in the panel member, a switch operator including a housing having a rear surface engaging the front surface of the second member and a movable portion having a free end spaced forwardly of the opening in the panel member and movable along the axis through the opening in the panel member, a collar including an internally threaded portion threaded on the externally threaded peripheral surface and a flanged front end extending forwardly of a front surface portion on the switch operator housing for maintaining the engagement between the front surface of the second member and the rear surface of the switch operator housing, a bushing having external surface portions tightly engaging portions of the second member and the first member for causing the flat surfaces of the second member and the first member to be respectively pressed into a tight engagement with the portions of the external and internal surfaces of the panel member and a bore extending through the bushing along the axis through the opening in the panel member, and a plunger extending through the bore with minimum clearance, said plunger having its opposite ends respectively engaging the free ends on the switch plunger and the operator member for transmitting movements of the operator member to the switch plunger whereby said internally mounted switch may be actuated by said externally mounted switch operator member while excluding the ingress of dust into said enclosure through the opening in said panel member.

2. The combination as recited in claim 1 wherein the panel member includes a pair of spaced openings, the first and the second members each include a pair of openings which are aligned with the pair of openings in the panel member, a pair of bushings have portions tightly engaging portions of the first and second members for pressing the flat surfaces of the members against surface portions of the panel member and a pair of plungers extending through bores in the bushings.

3. The combination as recited in claim 1 wherein the bushing has a threaded portion and a headed portion on its opposite ends respectively engaging a threaded portion on the second member and a surface portion on the first member.

4. The combination as recited in claim I wherein a non-rotatable connection between the second member and the external housing of the switch operator is provided by a pair of pins that project from a front face of the second member.

5. The combination as recited in claim 2 wherein each of the plungers has a headed portion that is engageable with free end of the switch operator.

6. The combination as recited in claim 2 wherein the switchoperator includes a pair of operator members each individually movable in the switch operator housing and having a free end engaging one of the pair of plungers for actuating one of a pair of switches that are positioned on the internal wall side of the panel member by the first member.

7. The combination as recited in claim 1 wherein the panel member is made of sheet metal and the switch operator is of the oil-tight type and the engagement between the flat surfaces on the first and second members and the internal and external surfaces of the panel member is sufl'iciently extensive to permit the enclosure to be classified as a dust-ignition-proof enclosure.

8. The combination as recited in claim 2 wherein a non-rotatable connection between the second member and the external housing of the switch operator is provided by a pair of pins that project from a front face of the second member.

9. The combination as recited in claim 2 wherein the switch operator is of the oil-tight type and the engagement between the flat surfaces on the first and second members and the internal and external surfaces of the panel member is sufficiently extensive to permit the enclosure to be classified as a dust'ignition-proof enclo- SUl'.

10. The combination as recited in claim 2 wherein the external housing of the switch operator has an externally threaded portion and a ring nut is threaded on the threaded portion. 

2. The combination as recited in claim 1 wherein the panel member includes a pair of spaced openings, the first and the second members each include a pair of openings which are aligned with the pair of openings in the panel member, a pair of bushings have portions tightly engaging portions of the first and second members for pressing the flat surfaces of the members against surface portions of the panel member and a pair of plungers extending through bores in the bushings.
 3. The combination as recited in claim 1 wherein the bushing has a threaded portion and a headed portion on its opposite ends respectively engaging a threaded portion on the second member and a surface portion on the first member.
 4. The combination as recited in claim 1 wherein a non-rotatable connection between the second member and the external housing of the switch operator is provided by a pair of pins that project from a front face of the second member.
 5. The combination as recited in claim 2 wherein each of the plungers has a headed portion that is engageable with free end of the switch operator.
 6. The combination as recited in claim 2 wherein the switch operator includes a pair of operator members each individually movable in the switch operator housing and having a free end engaging one of the pair of plungers for actuating one of a pair of switches that are positioned on the internal wall side of the panel member by the first member.
 7. The combination as recited in claim 1 wherein the panel member is made of sheet metal and the switch operator is of the oil-tight type and the engagement between the flat surfaces on the first and second members and the internal and external surfaces of the panel member is sufficiently extensive to permit the enclosure to be classified as a dust-ignition-proof enclosure.
 8. The combination as recited in claim 2 wherein a non-rotatable connection between the second member and the external housing of the switch operator is providEd by a pair of pins that project from a front face of the second member.
 9. The combination as recited in claim 2 wherein the switch operator is of the oil-tight type and the engagement between the flat surfaces on the first and second members and the internal and external surfaces of the panel member is sufficiently extensive to permit the enclosure to be classified as a dust-ignition-proof enclosure.
 10. The combination as recited in claim 2 wherein the external housing of the switch operator has an externally threaded portion and a ring nut is threaded on the threaded portion. 